The present invention relates to an apparatus for the continuous monitoring of the distance from the ground of overhead electric power line conductors.

The present invention is assembled on a supporting pylon of an electric power line and is advantageously used for effecting the continuous monitoring of the so- called ground clearance, i.e. the minimum distance that separates the ground from the lowest conductor of an overhead electric power line, to which the following description will make explicit reference, at the same time maintaining its generic characteristics.

The measurement of the height or ground clearance of spans of overhead lines is generally particularly important for allowing the optimization of the transporting capacity of overhead electric power lines.

As is known, the ground clearance of conductors of energy transporting lines depends on the temperature reached by the conductor, which in turn depends on the current circulating, the atmospheric temperature, wind, solar radiation and humidity.

With the same load of the electric power line, particular meteorological conditions such as, for example, a high environmental temperature, high solar irradiation, absence of wind and rainfall and low humidity, can lead to a temperature increase in various spans and, by thermal expansion, can cause an increase in the length of the conductor and consequently a lowering of the same conductor and a reduction in the ground clearance.

In order to avoid encountering problems associated with an excessive reduction in the ground clearance, at present the charge of the line is prudently limited on the basis of regulations that provide capacity values in relation to the climatic and seasonal region.

A great advantage would therefore be obtained from an optimum knowledge of the real behaviour of electric power lines in relation to environmental conditions and the charge .

Monitoring techniques currently known comprise the use of various temperature measurement apparatuses, assembled on the conductor, which require complex work on the part of electrical experts, due to the necessity of intervening on live line conductors in order to install the measurement instrumentation.

Optical instruments are available but have problems relating to the stability of the structure on which they are installed.

The objective of the present invention is to solve and overcome the problems of the known art indicated above .

In particular, an objective of the present invention is to provide a monitoring apparatus capable of effecting the control of the ground clearance of electric power lines, automatically and with a high time frequency, without the necessity of having to install complex instrumentations.

A further objective of the present invention is to provide an apparatus capable of monitoring the ground clearance with great precision, and that can be applied to an electric power line pylon, and on different spans .

Another objective of the present invention is to provide an apparatus which is free of deformations and movements of the pylon on which the instrument is installed.

The structural and functional characteristics of the present invention and its advantages with respect to the known art will appear more evident from the claims provided hereunder, and in particular from the following description, referring to the enclosed drawings, which show the schematization of a preferred but non-limiting embodiment of a monitoring apparatus, in which:

- figure 1 represents a schematic view of the monitoring apparatus object of the invention;

- figure 2 schematically represents the components of the measurement instrument to be installed on a pylon; and

- figure 3 is a schematic view of the apparatus of figure 1 in a particular arrangement of the pylons of the overhead electric power line.

With reference to figure 1, the number 1 indicates as a whole an apparatus for monitoring the distance from the ground of an overhead electric power line LE, which is defined by three conductors 2, 2a, 2b and 2c, respectively, with 2a situated above 2b and 2c, extending between two pylons 3 and 4 and defining a span C of said line LE.

More specifically, according to what is illustrated in figure 1, the apparatus 1 comprises a registering or viewing device 5, specified in detail hereunder in figure 2, assembled on the pylon 3 and suitable for registering and controlling the exact position of spherical, or ring or disk elements 7 with a retro- reflecting surface fixed around each conductor 2 (element 7a on the conductor 2a, element 7b on the conductor 2b, element 7c on the conductor 2c in figure 1) .

The spherical or bevelled form of the elements 7 and the positioning around the conductor reduces the crown effect and problems connected therewith to the minimum.

Further retro-reflecting elements 11a, lib or self- powered led light sources are installed on the pylon 4 opposite that 3 on which the system 5 is assembled and belonging to the same span C in order to effect a reference measurement.

According to what is illustrated in figures 1 and 2, the apparatus 1 comprises a device 5 defined by an insulated and watertight container B, containing in its interior a display group S comprising a camera 6 or videocamera with a telephoto lens, a computer PC with an acquisition card for the registration of images or alternatively a smartphone device for the acquisition of images and wireless pre-processing and transmission, an optical system 8 with LED sources for illuminating the retro-reflecting elements 7a, 7b, 7c, 11a and lib of figure 1 to allow shots to be taken by the photocamera 6.

An antenna 14 for the remote wireless transmission of data is present outside the container B.

The block 10 shown in figure 1 defines the self- power supply system, specified in greater detail in figure 2, and comprising a container A with a power supply system 12, batteries K and a photovoltaic panel 13 for the power supply.

The photovoltaic panel 13 is preferably but not exclusively installed externally on the container A, to which it is connected by means of an electric cable (not illustrated) .

The data and images can be sent to the ground to a remote wireless-type data acquisition and transmission device, schematized with a block 9 in figure 1.

The apparatus 1 of figure 1, when in use, is based on the automatic recognition of the position of the centre of gravity of the retro-reflecting elements 7, and operates in real time providing for example with wireless communication the device 9, or via telephone or website via satellite, with information on the position of the conductors 2 to a remote station (not illustrated) .

In order to allow a relatively high resolution of the position measurement, a digital photocamera 6 is used with a number of pixels equal to or higher than four Megapixel .

The lens of the photocamera 6 must reproduce the area that can be potentially occupied by the retro- reflecting elements 7 (about 10 x 10 m) on the sensitive element. For this purpose, a telephoto lens assembled on the photocamera 6 must be used.

During the day, the measurements do not require the use of LED sources, whereas during the night or under poor lighting conditions, LED sources of the device 8 with a concentrated beam are adopted, which prevalently illuminate the portion P of space (Figure 3) where the retro-reflecting elements 7 can move on the conductors and 11 on the opposite pylon.

In the case of rainfall, averages on consecutive images are effected in order to improve the signal/noise ratio.

The images are acquired through remote means, for example a cell phone such as a smartphone or a PC net, of the known type, equipped with internet connection for subsequent processing.

The apparatus 1 therefore allows the position of the centres of gravity of the retro-reflecting elements 7 assembled on the conductors 2 to be revealed with a precision of about five centimetres.

The measurements can be provided with a frequency of about a minute.

According to what is illustrated in figure 3, in order to allow the monitoring to be insensitive to the effect of possible variations in the axis of the pylons 3 and 4 with respect to the vertical due, for example, to strong wind and high thermal swings, further reference retro-reflecting elements, indicated with 11a and lib in figure 3, are assembled on the pylon 4 of the same span C opposite the pylon 3 on which the photocamera 6 is installed.

By comparison with a reference image taken at the beginning of the measurements where the initial positions of the retro-reflecting elements 11a and lib on the pylon 4 and the initial position of the elements 7a, 7b, 7c on the conductors 2, are registered, it is therefore possible to determine both the angular variation of the apparatus 1, i.e. the angle θι in figure 3 with respect to the initial position of the pylon 3 and also the movement of the elements 7a, 7b and 7c.

If the angular shift of the apparatus 1 is known, the contribution can be subtracted from this and the shift data of the elements 7a, 7b and 7c corrected, obtaining the correct ground clearance value.

The angular shift θ ₂ of the pylon 4 does not significantly influence, for realistic deformation angles of the pylon itself, the distances from the ground indicated with hi and h ₂ in figure 3 of the retro-reflecting elements 11a and lib.

When in use, once the apparatus 1 has been installed, the initial ground clearance value is established and is subsequently continuously updated by revealing the variations in the positions of the images of the elements 7a, 7b and 7c on the two-dimensional sensor of the photocamera 6.

The simplicity of the apparatus 1 described above reduces costs by installing numerous sensors on different spans of the electric power line LE .

The data are then sent to a remote computer for subsequent analysis of the evolution, with time, of the ground clearance and correlation with the charge data of the same line.